1. Field of the Invention
The present invention relates to a method of manufacturing a foamed product having a convexo-concave surface in which a foaming inhibitor is coated on or infiltrated into a surface of a foamable preform made of a foamable resin composition in a prescribed pattern and then the preform is foamed, and it further relates to a foamed product obtained through such a method and a material usable for such a method.
More specifically, the present invention relates to a liquid toner containing a foaming inhibitor, a method of a foamed product having a convexo-concave pattern involving a step where the foaming inhibitor is coated on or infiltrated into a surface of the foamable preform in a prescribed pattern though an electrostatic technique such as an electrostatic record or an electrostatic image transfer, and further relates to an intermediate product and a convexo-concave foamed product obtained though such a method.
2. Description of the Related Art
There has been known a printed product, an interior material and building material having a three dimensional pattern or a relief pattern, such as a foamed wall paper, a foamed flooring material or the like. They have been manufactured by a "chemical emboss" process. In the chemical emboss process, a foaming inhibitor is applied on a surface of a foamable preform made of a foamable resin composition in a prescribed pattern to form a pattern of a coating or infiltrated portion containing the foaming inhibitor, and then the foamable preform is foamed by heating or another manner. Thus a portion of the preform with no foaming inhibitor is foamed to rise or bulge while the other portion of the preform at which the foaming inhibitor is present is not foamed to be left unchanged, thereby forming a foamed product which has a surface provided with a convexo-concave pattern. The thus formed convexo-concave pattern is according to the pattern of the applied foaming inhibitor, and it makes up a three dimensional pattern (or a relief pattern) provided on the surface of the foamed product. The printed product and the other articles having a three dimensional pattern is manufactured through such a chemical emboss process. The chemical emboss process is disclosed in Japanese Patent Publication(Kohkoku) Nos. Sho 43(1968)-28636 and Japanese Patent Publication(Kohkoku) Nos. Sho 47(1972)-29187.
One of the known foamable resin composition is composed of polyvinyl chloride resin, a foaming agent such as azodicarbonamide, and a foaming accelerator such as zinc naphthenate. The foaming agent such as azodicarbonamide is decomposed by heating and generates gases such as carbon dioxide to form bubbles in the foamable resin composition. The foaming accelerator such as zinc naphthenate acts as a catalyst for decomposition of the foaming agent to lower a decomposition temperature. On the other hand, there has been used, as the foaming inhibitor, benzotriazole compounds or the like capable of inhibiting an effect of the foaming accelerator. When the foaming inhibitor is applied on the surface of the foamable preform made of the foamable resin composition, a foaming temperature of the portion retaining the foaming inhibitor gets higher than that of the other portion of the surface with no foaming inhibitor. Accordingly, if heating temperature of the foamable preform is controlled within at least a foaming temperature of the portion retaining no foaming inhibitor while under a foaming temperature of the portion retaining the foaming inhibitor, it is possible to foam only at the portion retaining no foaming inhibitor.
In the known art, the foaming inhibitor has been patternwise applied on the surface of the foamable preform by gravure printing, offset printing or the like, which need to use a form plate. Such a conventional process accordingly has suffered from a relatively long time and a large cost to make the form plate, whereby it has been involved in a problem that it is impossible to make preparation and evaluation of a prototype quick or smooth in a research and development stage.
As the other method substituting for the actual preparation of the prototype, it may be worth while considering a method in which a design of the surface of the prototype is generated and reproduced on a monitor through a digital process, and the thus reproduced image of the design is quickly output by means of an on-demand type printer such as an electrostatic plotter, an electrophotographic printer or the like to obtain a two dimensional sample of the design. When a sample of an ordinary printed product or publication is required, it is possible to generate and output an image very similar to a true image of a final product or a prototype in a short time by means of some digital proof printer, thereby carrying out preparation and evaluation of the proof in a sufficient mobility. However, since the foamed product having a convexo-concave surface largely varies its design or appearance including impression, texture or the like through the foaming process, even the digital proof printer can not generate the image very similar to the surface design of the final product or prototype. Accordingly it has been impossible to carry out an exact evaluation of the foamed product by this method.
For that reason, a designer or another product developer who studies the foamed product having a three dimensional pattern such as the wall paper, the foamed flooring or the like has not been allowed to prepare the prototypes frequently in the development stage, while he has been usually checked nothing but a montage image which is output by the digital proof printer and however reproduced not so exactly in order to perform the product development, and therefore it has been difficult to evaluate the design of the convexo-concave pattern of the surface in detail.
In addition, it is desirable for presentation of the foamed product to use a sample same as or very similar to an actual final product so as to demonstrate the design thereof sufficiently to the user. Preparation of the exact sample however needs to prepare the form plate for applying of the foaming inhibitor, thereby causing difficulties in time schedule and cost. Therefore, it has been difficult to perform the presentation of the foamed product in a sufficient mobility.